Anti-U3 RNP autoantibodies in systemic sclerosis

Arthritis Rheum. 2009 Apr;60(4):1112-8. doi: 10.1002/art.24409.


Objective: To describe the classification, demographic and clinical features, and survival in anti-U3 RNP autoantibody-positive patients with systemic sclerosis (SSc).

Methods: Medical records of 108 anti-U3 RNP-positive and 2,471 anti-U3 RNP-negative SSc patients first evaluated during 1985-2003 were reviewed. Anti-U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test.

Results: The anti-U3 RNP-positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti-U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti-U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti-U3 RNP-positive patients (25% versus 14%; P = 0.002), as was "intrinsic" pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and "renal crisis" did not differ significantly between the 2 groups. Survival was worse in the anti-U3 RNP-positive group (hazard ratio 1.38 [95% confidence interval 1.05-1.82]). PAH was the most common known cause of death in patients with anti-U3 RNP (30%, versus 10% in the anti-U3 RNP-negative group; P < 0.001).

Conclusion: The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti-U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti-U3 RNP-positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Autoantibodies / blood*
  • Black or African American / statistics & numerical data*
  • Female
  • Gastrointestinal Diseases / ethnology
  • Gastrointestinal Diseases / immunology
  • Gastrointestinal Diseases / mortality
  • Heart Diseases / ethnology
  • Heart Diseases / immunology
  • Heart Diseases / mortality
  • Humans
  • Hypertension, Pulmonary / ethnology
  • Hypertension, Pulmonary / immunology
  • Hypertension, Pulmonary / mortality
  • Male
  • Middle Aged
  • Pulmonary Fibrosis / ethnology
  • Pulmonary Fibrosis / immunology
  • Pulmonary Fibrosis / mortality
  • Ribonucleoproteins, Small Nucleolar / immunology*
  • Scleroderma, Systemic / ethnology*
  • Scleroderma, Systemic / immunology*
  • Scleroderma, Systemic / mortality
  • Seroepidemiologic Studies
  • Sex Distribution
  • Skin Diseases / ethnology
  • Skin Diseases / immunology
  • Skin Diseases / mortality
  • Survival Analysis
  • White People / statistics & numerical data*


  • Autoantibodies
  • Ribonucleoproteins, Small Nucleolar
  • ribonucleoprotein, U3 small nucleolar